Vented heater appliances are well known and commonly used in residential dwellings and other structures for heating and esthetic purposes. Examples include gas-burning furnaces and gas-burning and wood-burning fireplaces. Traditional wood-burning fireplaces are not particularly efficient heaters, they tend to be dirty and require frequent cleaning due to the nature of the fuel used, and they require a constant supply of wood or other fuel. In view of the disadvantages of traditional wood-burning fireplaces, there has been a move to cleaner and more efficient gas-burning fireplaces.
Top-vent and direct-vent fireplaces make up the majority of gas-burning fireplaces sold in the United States. A top-vent fireplace vents exhaust to the outside and draws combustion air from the surrounding room. Direct-vent fireplaces draw combustion air from outside of the structure and vent exhaust gas to the outside using either a duct-within-a-duct arrangement or two separate ducts. Direct-vent fireplaces are either a free-standing style or a fireplace insert style positionable into a fireplace cavity built into the wall of a house, apartment, condominium, or other residential dwelling or structure. These direct-vent fireplaces are connected to suitable combustion air and exhaust gas ducts that communicate with the exterior of the dwelling.
FIG. 1 is a schematic side-elevational view of a conventional direct-vent fireplace insert installation in accordance with the prior art. The direct-vent fireplace insert 100 is situated within a preformed fireplace cavity 112. Windows 122 may be provided on the insert 100 for viewing a fire 123 within a firebox 110. The insert 100 is connected to an exhaust duct 114, which is routed through a chimney 118 that communicates with the fireplace cavity 112. The illustrated fireplace insert 100 is also connected to a combustion air intake duct 116 concentrically disposed around the exhaust duct 114. In an alternate embodiment, the exhaust duct 114 can be spaced apart from the intake duct 116 so that the exhaust duct is not inside the intake duct.
Direct-vent fireplaces require a balanced flow of combustion air and exhaust gas moving through the intake and exhaust ducts 116 and 114, respectively, to provide an aesthetically desirable flame in the firebox 110. Desirable flame characteristics can include, for example, appearing similar to a natural wood-fire flame. The size, color and action of the flames in the firebox 110 can be adjusted by selectively balancing the flow of combustion air and exhaust gas. A balanced flow also allows direct-vent fireplaces to function in a thermally efficient manner. Accordingly, an important part of the fireplace insert's installation is to properly balance the combustion air intake flow and the exhaust gas flow.
The conventional insert-style fireplace insert 100 is typically installed and balanced by first sliding the insert into a close-fit fireplace cavity 112 so a limited access space 126 is provided between the fireplace insert and the cavity's walls. The installer reaches through the limited access space 126 to connect the fireplace insert to the exhaust duct 114 and the intake duct 116. The installer then balances the flow of combustion air and the exhaust gas while the fire 123 is burning in the firebox 110 in order to visually analyze the flame characteristics. Limited access to the adjustment mechanisms for the intake duct 116 or the exhaust duct 114 can make this balancing a time-consuming and labor intensive process requiring multiple adjustments of the adjustment mechanisms during installation.